ZCS + Funambol + Outlook + Calendar problem

OK, short introduction: My brother and I have been using Zimbra (open source edition) as our mail server for a couple years now. Currently, we're partnering with some other folks, and looking to expand our collaboration capabilities, and one of the goals is to have shared calendars for everyone.

To this end, I decided to go ahead and migrate the folks we're partnering with over to our mail server, so we could all be able to easily see each others' calendars. Managing these remotely was easy for me, since I use Thunderbird and Lightning. However, the other folks are using Outlook for their calendaring stuff, and Outlook only seems to support grabbing events from the Zimbra calendar, but not allowing the user to add events in Outlook and then have them sent to Zimbra.

A little bit of research seemed to indicate that while Outlook was capable of publishing calendar events via WebDAV, this was not supported by the Zimbra open source edition. Since we'd been looking at Funambol for a while anyway for the mobile syncing stuff, I decided to roll with that and see if I could use it as an intermediary between Outlook and Zimbra.

Long story short, Funambol is now functional with my mobile device, and mostly functional with Outlook. However, like the previous situation, Funambol seems to only be able to pull events from Zimbra and send them to Outlook. Trying to publish events from Outlook to Zimbra gets me a message informing me that items failed to update on the server. Contacts will sync both ways with no problems; this only happens with calendar stuff.

If anyone has any ideas here, I'd appreciate any input. I know that I have alternatives, such as getting folks to either switch local clients or else use the Zimbra web interface, but I'd prefer to get this working, partially because I've put a fair amount of time into it, and I'd rather not come back and allow as to how I've essentially achieved nothing save for failure in that time.